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Reference signal generator

Active Publication Date: 2017-11-23
FURUNO ELECTRIC CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent text describes a way to reduce the phase noise of an oscillator caused by the quantization error of a D / A converter. This is achieved by shifting the frequency of the oscillator to a higher range using oversampling of the modulator, and then cutting it with a low-pass filter. The technical effect is to improve the accuracy and stability of the oscillator.

Problems solved by technology

With the above configuration, due to various causes such as a position of a GNSS satellite, an obstacle, an interfering radio wave, or any failure of a GNSS antenna, the GNSS receiver may fail to receive a signal from the GNSS satellite and generate the reference signal.

Method used

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  • Reference signal generator
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Experimental program
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first embodiment

[0038]Next, embodiments of this disclosure are described with reference to the drawings. FIG. 1 is a block diagram illustrating a reference frequency generator 10 according to this disclosure. FIG. 2 is a block diagram illustrating a configuration of a delta-sigma modulator 15.

[0039]The reference frequency generator (reference signal generator) 10 of the first embodiment of this disclosure may be used in a base station of mobile phones, a transmitting station of terrestrial digital broadcasting, and a WiMAX (Worldwide Interoperability for Microwave Access) communication facility, and may provide a reference frequency signal and a reference timing pulse to a user-side device connected thereto.

[0040]As illustrated in FIG. 1, the reference frequency generator 10 of the first embodiment may include a voltage controlled oscillator (oscillator) 17, a frequency divider 18, a phase comparator 12, a loop filter (phase difference signal converter) 13, a switch circuit 14, the delta-sigma modu...

second embodiment

[0085]The reference frequency generator 10x of the second embodiment is intended to solve the above problem. For example, in the phase synchronization circuit 25 of the reference frequency generator 10x, a low-pass filter (filter) 19 may be disposed in a stage subsequent to the D / A converter 16 and precedent to the voltage controlled oscillator 17.

[0086]With the configuration of this embodiment, (similarly to the first embodiment described above,) in the phase synchronization circuit 25 which is a digital PLL circuit, the delta-sigma modulator 15 may modulate the control voltage signal outputted from the loop filter 13. In this embodiment, oversampling may be performed by the delta-sigma modulator 15.

[0087]Generally, when oversampling is performed by a delta-sigma modulator, a transfer function with respect to the quantization error is known to be small within a low frequency range, and large within a high frequency range. Therefore, quantization noise components of the output signa...

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Abstract

In a reference signal generator including a synchronization circuit configured to convert a digital signal into an analog signal, supply this signal to a voltage controlled oscillator, and control the voltage controlled oscillator to obtain a signal synchronized with the reference signal, without an accumulation of quantization error in a holdover control in which an acquisition of a reference signal is not available. The reference signal generator includes a phase synchronization circuit and a controller. The phase synchronization circuit controls the reference signal outputted from the oscillator, according to a control signal obtained based on the reference signal. The controller generates a free-running control signal and controls the oscillator when the reference signal becomes unavailable. The oscillator receives discrete values and oscillates accordingly. A digital delta-sigma modulator configured to modulate the free-running control signal of the controller disposed in a subsequent stage of the controller.

Description

TECHNICAL FIELD[0001]This disclosure relates to a reference signal generator, which controls an oscillator to synchronize a reference signal with a reference signal.BACKGROUND ART[0002]For example, in base stations of mobile phones and transmitting stations of digital broadcasting, a highly accurate reference frequency signal (reference signal) required for synchronizing a timing and frequency of signal transmission is supplied using a reference frequency generator (reference signal generator). This type of reference frequency generators includes a reference frequency generator which controls a voltage controlled oscillator to synchronize an output signal with a highly accurate reference signal obtained from a GNSS receiver, and outputs the reference frequency signal.[0003]This voltage controlled oscillator is configured to generate different frequencies according to an inputted control voltage. One example of such a voltage controlled oscillator is an analog type using a quartz cry...

Claims

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Application Information

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IPC IPC(8): H03L7/099H04L7/04H03L7/091
CPCH03L7/0992H04L7/04H03L7/091H03L7/14H03L7/0805H03L7/0807H03L7/143H03L7/189H04L7/0029H04L7/0331
Inventor HASHIMOTO, KUNIHIKO
Owner FURUNO ELECTRIC CO LTD